1. Field of the Invention
This invention relates to a process and an apparatus for considerably reducing an iron loss of a magnetic material such as grain oriented electromagnetic steel sheets, amorphous material or the like used in transformers and so on.
2. Related Art Statement
The iron loss of the grain oriented electromagnetic steel sheet is a heat energy loss generated from the steel sheet in use as a core of a transformer or the like. Lately, a demand for reducing the heat energy loss, i.e. the iron loss of the grain oriented electromagnetic steel sheet is increasingly enhanced in view of energy-saving.
In order to reduce the iron loss, there have been made various attempts such as high alignment of crystals of steel sheet into {110}&lt;001&gt; orientation, rising of Si amount for increasing electrical resistance of steel sheet, decreasing of impurities, and further thinning of steel sheet gauge. However, the reduction of iron loss by these metallurgical methods substantially gets to a limit.
Therefore, there are proposed some methods for improving the iron loss in addition to the metallurgical method. Among them, a method of reducing the iron loss through the irradiation of a pulsed laser beam as disclosed in Japanese Patent Application Publication No. 57-2,252 or the like is actually industrialized at present. Such a method makes possible to largely reduce the iron loss as compared with the conventional methods, but can not avoid the increase of initial cost and running cost due to the fact that the equipment used is expensive and the service life of a lamp for exciting the laser beam is not long. Moreover, the laser beam used is not usually a visible ray, so that a safety means must be taken.
Furthermore, a method of irradiating a continuous laser beam is disclosed in Japanese Patent laid open No. 59-33,802 and No. 59-92,506. This method has the same drawback as in the case of the pulsed laser beam as well as drawbacks that the effect of iron loss reduction is small, the laser beam absorbance of the steel sheet inevitably changes to obtain no constant effect.